The present invention generally relates to the manufacture of pipe, and particularly of culvert or corrugated pipe, on an economic basis to minimize or eliminate pipe handing and storage or inventory costs while providing the customer with service.
In the past pipe, and particularly culvert pipe was spirally wound on one or a few helical pipe forming machines installed in a plant. U.S. Pat. No. 3,247,692 describes an exemplary pipe making machine which is presently in use. Such machines receive pipe forming devices which engage an elongate strip of corrugated metal and helically wind the strip to form the pipe. A separate forming device is required for each pipe diameter, and it was customary to run the machine for a period of time to produce an inventory of pipe of a given diameter. Thereafter the machine is changed over for the production of another pipe diameter by replacing the forming device with another forming device dimensioned to produce pipe of such other diameter.
The changeover is time consuming and represents machine and plant down-time which is expensive and adds to the cost of the pipe. Moreover, the changeover requires a precise alignment of parts which in turn necessitates highly skilled labor. Inaccuracies in the alignment could result in the production of pipe which exceeds the permissible tolerance and which must, therefore, be rejected. Furthermore, misalignments frequently cause disproportionate wear and tear of parts of the forming device which in turn requires premature and costly replacement of such parts.
In addition to the relatively large operating expenses conventional plants require that a substantial pipe inventory be kept on hand so that customers can be efficiently served. The inventory must be stockpiled with at least the most popular pipe sizes and pipe lengths. Since each pipe diameter must be stocked in a plurality of lengths the overall inventory is large and represents a substantial capital investment. Furthermore, the stocking, maintaining, and use of the inventory requires the multiple handling equipment such as cranes, fork lifts, transportation vehicles and the like. In sum, therefore, the costs of manufacturing pipe along conventional lines were significantly increased by the need for frequent pipe forming machine changeovers, the need for highly skilled labor to effect such changeovers, capital investments in large inventories and capital investments in the necessary labor and equipment to service such inventories.